been Dazed and Confused

[Shred Astaire]

What O-rings?

Number 3

https://www.partzilla.com/catalog/suzuki/motorcycle/1978/gs750ec/front-caripers-gs750ec

[allojohn]

Number 3

https://www.partzilla.com/catalog/su...ripers-gs750ec

As Ed says, check the return breather hole in the master cylinder. When bleeding doesn’t work it’s pretty much always the return breather that’s blocked.

[Shred Astaire]

As Ed says, check the return breather hole in the master cylinder. When bleeding doesn’t work it’s pretty much always the return breather that’s blocked.

Which hole is that?

[Shred Astaire]

http://www.youtube.com/watch?v=ZQgYn23Xvck

Just ordered a new rebuild kit for the front master, an O Ring for the well and a couple of new axle O Rings for the calipers so I can switch them around. If that doesn't work I'll go for the new lines. They be expensive.

RIP Gary, Nobody with faster fingers on earth.

https://www.youtube.com/watch?v=aW9hCIiZ-gE

[Nessism]

O-rings on the slide caliper pins won't affect fluid flow into the caliper. Those are nowhere near the fluid.

I wonder if your lines or splitter is blocked somewhere? The banjo bolts often fill up with system sludge.

[Shred Astaire]

O-rings on the slide caliper pins won't affect fluid flow into the caliper. Those are nowhere near the fluid.

I wonder if your lines or splitter is blocked somewhere? The banjo bolts often fill up with system sludge.

Thanks Ed, I'll check that out. What I don't get is how the fluid is pumping just as good as the back did but the front won't firm up. I'm tempted to wrap the whole system in seran wrap and look for an air bubble. No leaking anywhere and fluid flowing nicely as we keep refilling the well. I don't know if you saw my comment about pitting. It's on the rear of the master cylinder at the banjo outside surface. I'm wondering if it was inside also and air is escaping the handle side of the cylinder.

[allojohn]

Which hole is that?

At the bottom of the fluid reservoir, you'll need to completely dismantle it.

[Shred Astaire]

At the bottom of the fluid reservoir, you'll need to completely dismantle it.

I clean as I go and when I did the master cylinder (off the bike) I took the well off and cleaned everything in and on the master and got a new front brake switch in case it was part of the main system. I wasn't sure if it was part of this problem as the wire wasn't attached and it was just an empty rectangle hole under the brake lever. I started this front brake problem over a month ago.

[Big T]

When you look down into the reservoir, you'll see a small hole and, when you pump the lever, you can see some movement in there.That's the feed hole.

Just towards the hose end of the MC is a really small hole. That's the pressure relief hole. When you pump the lever and release, there should be a small spurt from that hole. No spurt, the hole is blocked

[Shred Astaire]

When you look down into the reservoir, you'll see a small hole and, when you pump the lever, you can see some movement in there.That's the feed hole.

Just towards the hose end of the MC is a really small hole. That's the pressure relief hole. When you pump the lever and release, there should be a small spurt from that hole. No spurt, the hole is blocked

Ok, I'll take the plate w/2 screws out of the reservoir and check the hole taking fluid to the MC. Then I'll take the banjo bolt/hose off the end of the MC and look inside for another hole?

[Nessism]

If you are pumping lots of fluid through the system as you say then the master must be pumping. What happens if you take the lines loose at the calipers and pump? Do you get strong fluid flow? If so that points at the calipers as being the problem.

[Shred Astaire]

If you are pumping lots of fluid through the system as you say then the master must be pumping. What happens if you take the lines loose at the calipers and pump? Do you get strong fluid flow? If so that points at the calipers as being the problem.

Thanks Ed! I need to take the hose system apart and clean it out and blow some air through there in case there is old crusty dried fluid in the lines. When I got the bike, there was no fluid in the tank and some dried out fluid to clean out. The fluid pumping out is all clean and clear at this time. I have one of those translucent hose/cup bleeders.

[Shred Astaire]

If you are pumping lots of fluid through the system as you say then the master must be pumping. What happens if you take the lines loose at the calipers and pump? Do you get strong fluid flow? If so that points at the calipers as being the problem.

I was reading the service manual today and read that I was supposed to put grease on the outer edges of the inner brake pad that rides in the carriage. I didn't do that.

[oldGSfan]

Long ago I had a CB750 with single front disc and had all kinds of trouble getting it bled. Then similar probs on a 79 CB750 Limited Edition. Both had were original lines, 15 or 20 years old or so, but rebuilt calipers and MC. It was so frustrating, I spent hours and hours. I eventually had some luck with bungee cording the lever to the bar (or to the point where the air could come up and through) until tiny bubbles floated through the MC - eventually. I'd get excited to see one little bubble. I got it 'good enough' to ride and eventually they firmed up more with use but were never really that great.

My most recent experience with the GS1100E was the opposite. I put Earl's brake lines on, with info from the tutorial on here, and used a Harbor Freight vacuum (Mityvac type of tool) to pull the fluid through, and bam, they were perfect in about three pulls each, front and rear. I got a little packet of silicone brake grease at the local auto parts store and treated the sliding surfaces/pins. I didn't treat the seals with the grease, just fluid. My calipers and pistons were pristine so that helps too. I used DOT4 after reading that DOT5 may trap more bubbles. I used the much maligned K&L kits, not OEM stuff, but they work as good as new. I got them before I read up on them here but I guess I lucked out (so far). I have more $ and less patience, plus better tools now. Also YouTube and forums are so great, I didn't have those.

If you use a vacuum pump it may be better because it pulls large amounts through in one shot, rather than incrementally pushing a bit down. I've had mixed results with vac pumps in the past but this time was perfect - I use grease around the bleeder threads to help with air seeping in that way, which mainly helps with visually knowing they are done. Oh - I actually hoisted my old Honda's front end up so the bike was nearly vertical, I was trying every trick in the book.

Just thought I'd share as I feel your pain. I think several things are at play and all add up, I can't point to one but for safety the lines seem key.

[2BRacing]

Ok, I'll take the plate w/2 screws out of the reservoir and check the hole taking fluid to the MC. Then I'll take the banjo bolt/hose off the end of the MC and look inside for another hole?

No, the tiny return hole is also at the bottom of the reservoir below the plate, but about 1/4 to 1/2 inch away from the larger feed hole towards the banjo bolt side.

The return hole is only about the size of a pin, so crud may be concealing it.

Nobody has commented about the following statement in your post #6: Another oddity that has happened twice now is, the great suction holding the cap on the fluid well the next day after a bleeding session. I have to use all of my 64 yr old muscles to remove the damn cap.

If this is still happening, it is really odd, because there should not be suction (vacuum) in the fluid reservoir that can make the cap difficult to remove. Possibly this is another clue that the tiny return hole could be blocked, but I have never heard of suction building up in the reservoir, so my guess could be way out of line!

Good luck with getting your brakes working properly.